Immunotherapy, in medicine, refers to an array of treatment strategies based upon the concept of modulating the immune system to achieve a prophylactic and/or therapeutic goal.

Cancer

Cancer immunotherapy attempts to stimulate the immune system to reject and destroy tumors. BCG immunotherapy for early stage (non-invasive) bladder cancer utilizes instillation of attenuated live bacteria into the bladder, and is effective in preventing recurrence in up to two thirds of cases. Topical immunotherapy utilizes an immune enhancement cream (imiquimod) which is an interferon producer causing the patients own killer T cells to destroy warts, actinic keratoses, basal cell cancer, squamous cell cancer, cutaneous lymphoma, and superficial malignant melanoma. Injection immunotherapy uses mumps, candida or trichophytin antigen injections to treat warts (HPV induced tumors).

Dendritic cell based immunotherapy

This utilizes dendritic cells to activate a cytotoxic response towards an antigen. Dendritic cells, an antigen presenting cell, are harvested from a patient. These cells are then either pulsed with an antigen or transfected with a viral vector. The activated dendritic cells are then placed back into the patient; these cells then present the antigens to effector lymphocytes (CD4+ T cells, CD8+ T cells, and in specialized dendritic cells, B cells also). This initiates a cytotoxic response to occur against these antigens and anything that may present these antigens. One use for this therapy is in cancer immunotherapy. Tumor Antigens are presented to dendritic cells, which cause the immune system to target these antigens, which are often expressed on cancerous cells.

T cell based adoptive immunotherapy

This therapy uses T cell-based cytotoxic responses to attack cancer. In brief, T cells that have a natural or genetically engineered reactivity to a patients' cancer are expanded in vitro using a variety of means and then adoptively transferred into a cancer patient. T cells with a natural occurring reactivity to a patient's cancer can be found infiltrated in the patients' own tumors. The tumor is harvested, and these tumor infiltrating lymphocytes (TIL) are expanded in vitro using high concentrations of interluekin-2 (IL-2), anti-CD3 and allo-reactive feeders. These T cells are then transferred back into the patient along with exogenous administration of IL-2. Thus far, a 51% objective response rate has been observed; in some patients, tumors shrank to indetectable size. In the case of engineered T cells, T cell receptors (TCR) that have been identified to have reactivity against tumor associated antigens are cloned into a replication incompetent virus that is capable of genomic integration. A patients own lymphocytes are exposed to these viruses and then expanded non-specifically or stimulated using the engineered TCR. The cells are then transferred back into the patient. This therapy has been demonstrated to result in objective clinical responses in patients with refractory stage IV cancer. The Surgery Branch of the National Cancer Institute (Bethesda, Maryland) is actively investigating this form of cancer treatment for patients suffering aggressive melanomas.